Browse Prior Art Database

# Signature Segmentation

IP.com Disclosure Number: IPCOM000088761D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 4 page(s) / 100K

IBM

## Related People

Anthony, NJ: AUTHOR [+1]

## Abstract

The Signature Segmentation (SS) procedure described herein receives, as input, a sequence of pressure readings p(1), p(2), ..., p(n) taken at equal time intervals t(i) =(i-1) delta t, i=1,2,...,n, from a pressure-detecting stylus while an individual is signing a signature. SS outputs a set of pairs of times (tau(1),tau(2)),..., (tau(2k-1), tau(2k)), where tau(2i-1) is the i-th time the pen contacted the paper and tau(2i) is the i-th time the pen was lifted up from the paper. Fig. 1 shows a pressure curve p(t), the points t(1),t(2),...,t(n) at which p(t) was sampled and the pairs (tau(1),tau(2)), ... determined by SS. Arrows pointing downward imply pen contact with paper; arrows pointing upwards imply pen lifted up from paper.

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Signature Segmentation

The Signature Segmentation (SS) procedure described herein receives, as input, a sequence of pressure readings p(1), p(2), ..., p(n) taken at equal time intervals t(i) =(i-1) delta t, i=1,2,...,n, from a pressure-detecting stylus while an individual is signing a signature. SS outputs a set of pairs of times (tau(1),tau(2)),..., (tau(2k-1), tau(2k)), where tau(2i-1) is the i-th time the pen contacted the paper and tau(2i) is the i-th time the pen was lifted up from the paper. Fig. 1 shows a pressure curve p(t), the points t(1),t(2),...,t(n) at which p(t) was sampled and the pairs (tau(1),tau(2)), ... determined by SS. Arrows pointing downward imply pen contact with paper; arrows pointing upwards imply pen lifted up from paper.

In practice, pressure curves are not as simple and clearly defined as the example of Fig. 1. Figs. 2 and 3 show two examples of pressure curves which have been obtained in the laboratory.

In both of these curves the pairs (tau(2i-1),tau(2i)) must be determined not from the intersection of p=p(t), p=0 but from the intersection of p=p(t),p=c(1) (Fig.
2) and p=p(t), p=c(2) (Fig. 3).

The problem then, in general, is to determine for each pressure curve p(t) the correct pressure level p=c, such that the intersection of p=p(t) and p=c gives the correct pairs (tau(2i-1),tau(2i)).

The SS procedure is in four steps:
1. Computation of a working minimum pressure p=c(min) based on

local extrema of p(t).
2. Transformation of p(t) into p*(t) with corrected baseline and

spikes removed. For example, depressions in p(t)

which suggest pen-up, pen-down movements

are made more pronounced (deeper) in

p*(t) (Fig. 4). Spikes (as in Fig. 3) which clearly

do not belong in p(t) are removed in p*(t) (Fig. 5).
3. Using p*(t) and its derivative with respect to time,

D(t)p*(t),

segmentation times candidates are obtained:

(t(i(1)), t(i(2))),...,(t(i(k)), t(i(k+1))).

These times are determined from D(t)p*(t)

by keeping track of when...